Rhizophydium littoreum on the Eggs of Cancer anthonyi: Parasite or Saprobe?

The relationship between host and symbiont is often difficult to assess and quantify. A novel technique that may help assess the host-symbiont relationship of organisms found in crab egg masses is described. This technique may have application in determining the relationship of other host-symbiont associations. Crab eggs were killed cryogenically and exposed in combinations with live eggs to a previously unreported symbiont of crab egg masses. The results indicated that the chytrid Rhizophydium littoreum is primarily a saprobe that attacks dead eggs; yet at high zoospore densities, it attacks and kills live eggs. Furthermore, R. littoreum is the first chytridiomycete to be reported from a marine crustacean host. It was highly prevalent on the eggs of its host and was found throughout the year.